Vibratory conveyors are widely used for material handling, and typically include a generally elongated conveyor bed, and an associated vibratory drive. Operation of the vibratory drive induces vibratory motion in the conveyor bed, which motion in turn induces movement of articles along the bed. Vibratory drives for such devices typically include one or more pairs of counter-rotating shafts having eccentrically-mounted weights thereon for inducing the desired vibration of the conveyor bed.
One type of vibratory conveyor arrangement, sometimes referred to as a four shaft differential motion conveyor, includes a vibratory drive including first and second pairs of counter-rotating drive shafts, with one pair of drive shafts operated at twice the speed of the second pair. This type of vibratory drive arrangement has been found to induce substantially planar, slow forward and fast rearward motion, which is well suited for gentle handling of delicate materials, such as potato chips, flaked cereals, and the like. In this arrangement, the vibratory drive is configured such that the half-speed and full-speed drive shafts are synchronized, or operated in phase, such that the vibratory forces induced by the eccentrically mounted weights cyclically add in one direction, and cyclically subtract in the other direction. The drive is configured such that the addition of vibratory forces acts in the direction opposite to the material flow, causing a fast pull-back of the conveyor bed. In contrast, the vibratory forces subtract from one another in the direction of material flow, thereby causing the vibratory bed to slowly move forward in the direction of material feed.
The present invention contemplates an arrangement whereby eccentric weights of a differential motion vibratory drive are configured to provide out-of-phase inducement of vibratory motions, thereby substantially increasing the feed rate of material being conveyed, without any change in the rotating and balance of the shafts of the drive.